Low Mill outdoor centre by any chance? If it is, its an awesome place.
I think that's the place
The following are relatively close:
Devis Hole Mine
Windegg Mine Caverns - a gem that everybody has to do (once)
Sir Fransis Level
Pasture Gill Pot
Hagg Gill Pot
Otters Cave (for any divers)
I've been to Devis Hole a couple of times and visited most a lot of the Swaledale mines. I actually saw in my 21st birthday at midnight in the engine chamber of Sir Francis Level, with a bottle of bubbly, nicely cooled by the deep water on the way in
Also done a bit in Wharfedale, so I'll probably give those a miss and stick to Wensleydale for the novelty.
Crackpot I've heard of (recent CNCC conservation works?), but not been to, so it sounds like that's on the list.
Where is Otters Cave? Can't see it on the CNCC website...